Rotating Electrical Machine Rotor Flange for Noise Reduction
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Solution Overview
Problem
Permanent-magnet-type rotating electrical machines with concentrated windings experience electromagnetic excitation force resonances at specific revolutions, leading to noise due to low-order harmonic components, and existing methods struggle to minimize these forces without compromising voltage suppression capabilities.
Innovation Solution
The design incorporates a stator with teeth having a central winding section, a tip section without windings, and a flange between them, where the flange is formed outwardly as an arc with a specific radius, allowing for minimized electromagnetic excitation force when driven with a negative d-axis current at resonant frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If concentrated winding is used in the stator, then the axial length of the rotating electrical machine can be shortened, but electromagnetic excitation force of low-order deformation mode occurs due to low-order harmonic components
Solution Approach 1:
The invention applies local quality by creating a non-uniform air gap structure through protrusions on the rotor yoke. Specifically, protrusions are formed at specific positions (e.g., at the N-pole and S-pole centers) to locally modify the air gap length. This local modification changes the magnetic flux distribution in those specific regions, thereby suppressing low-order harmonic components and reducing electromagnetic excitation force while maintaining the concentrated winding structure and short axial length.
2Use of energy by moving object
If negative d-axis current is increased to suppress voltage during high-speed rotation, then voltage suppression is improved, but electromagnetic excitation force increases at resonant frequencies
Solution Approach 1:
The invention applies preliminary action by pre-configuring the rotor yoke with protrusions that are positioned in advance to counteract the electromagnetic excitation force. These protrusions are designed with specific dimensions and positions (e.g., extending radially outward by a predetermined length at the N-pole and S-pole centers) to create a magnetic flux distribution that opposes the low-order harmonic components before they can cause resonance. This allows the use of smaller negative d-axis current while still achieving voltage suppression and reducing electromagnetic excitation force at resonant frequencies.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration enables the machine to be driven with a negative d-axis current that minimizes electromagnetic excitation force, reducing noise and maintaining operational stability at revolutions matching the resonant frequency of machine parts.
Implementation Method 1
a rotor 4 that forms a magnetic field using permanent magnets 21
Implementation Method 2
the magnetomotive force generated by the stator windings includes low-order harmonic components that do not contribute to torque
Implementation Method 3
the flange 12 is formed outward of an arc having, as the radius thereof, a distance from a second intersection point of an inner peripheral face of the stator and a straight line that joins a rotation axis of the rotor and the first intersection point
Data Source
AI summary
Given a first intersection point of the surface of a rotor and a straight line that joins a central point of a permanent magnet on a stator side and a tooth tip section closest to the central point of the permanent magnet on the stator side, a flange is formed outward of an arc having, as the radius thereof, a distance from a second intersection point of the inner peripheral face of the stator and a straight line that joins the rotation axis of the rotor and the first intersection point, up to the tooth tip section.